it would be FAR too expensive to store that much data on that many people for that long period of time. all they really do is look for keywords or phrases related to terrorism, none of it is actually stored. it goes in, is checked for threats or dangerous plots, then goes into a hold period for a few months where a second scan is run, then after that its deemed irrellevent information and discarded

Dude, we have $5 flashdrives that store 16GB of data. That's after increasing the price to may the retailer for distribution. 16 gigs can store a lot of data, just think how much internet history can be stored if they only spent $100,000 on storage. Considering your history can be stored as a text file, that's a lot of people's history for quite a long time. Money is of no issue.

Actually storage on a mechanical hard drive can cost less than 0.05 cents per a gigabyte so 100,000 dollars can get you 2000 terabytes of data storage (note this is a rough estimation and costs of servers with redundancy will add a hell of alot more to the price tag)